Posted
by
timothy
on Saturday August 13, 2011 @10:22PM
from the put-the-new-toys-on-the-credit-card dept.

itwbennett writes "Even the most ardent enthusiasts gathered at the annual Space Elevator Conference on Friday don't expect it to be built anytime soon, but that doesn't stop them from dreaming, planning, and trying to solve some of the more vexing problems. One of the trickiest questions is who's going to pay for the operational costs when an elevator is eventually built. 'It's been nine years we've been looking for someone' to study that, said Bryan Laubscher, one of the leading space elevator enthusiasts and principle at Odysseus Technologies, a company working on high-strength materials."

It needs to be strong but nanotubes aren't required. You make a cable about 1000 km long. It has fittings on both ends which vehicles can attach themselves to. It orbits slightly more than 500 km above the ground and rotates its its axis horizontal and at 90 degrees to its orbit. The length and orbital altitude and chosen so that when one end almost reaches the ground it has a low velocity, while the other end is above escape velocity. You use it to exchange mass between the surface of the Earth and a trajectory which will take you to other planets. A dead mass can be sent down to Earth and a vehicle carrying passengers and supplies can be sent the other way.

The idea is tantamount to expecting to go to the moon by pulling on your own boot straps.

In order for it to work, you'd need to have some energy source to resist the pull of the item you're wanting to lift into space. And by the time you start sending rockets up with fuel to do that, you might as well just use rockets to send the payload into orbit because it's much more efficient.

Well, one idea is that you catch random orbiting junk at the other end, replenishing the lost momentum. In any case, efficiency isn't particularly important. The major limitation on getting things into space right now is construction, launch logistics, etc. If we could somehow be continuously sending things into space, it would be well-worth having to send two or three times the fuel along with.

The idea is tantamount to expecting to go to the moon by pulling on your own boot straps.

In order for it to work, you'd need to have some energy source to resist the pull of the item you're wanting to lift into space. And by the time you start sending rockets up with fuel to do that, you might as well just use rockets to send the payload into orbit because it's much more efficient.

There's power aplenty at the orbit, so just use ion or plasma propulsion, and send stuff up at frequency that matches the average lift generated. The amount of propellant sent up will be a tiny fraction of what current chemical rockets need to get a single kilogram to orbit. And if more capacity, more frequent lifts, are needed, then just strap on more engines, and/or send more stuff down to earth.

Orbits come in many sizes. Orbits close to geostationary orbits have the following properties:if you are slightly closer to earth, you will fall down (slowly)if you are at the exact right spot, you will stay thereif you are slightly further away from earth, you are in effect on an escape trajectory, you will gain height (slowly)

So here's an idea. Since this cable has to withstand umpteen giganewtons of tension anyway, place the top of the elevator too high. The

thats a stupid idea. the sheer drag as it plows through the atmosphere repeatedly means itll last only a few orbits, if that. even if the speed was low, the drag would still be large enough to bring it down quickly. and anything you sling into orbit is gonna pull the entire thing down, so your gonna need the same, probably more, thrust to bring it back to that 500km orbit than youd spend just blasting a rocket with that payload on the same trajectory.

thats a stupid idea. the sheer drag as it plows through the atmosphere repeatedly means itll last only a few orbits, if that.

I'm not entirely convinced. If you rotate it at the correct speed it could have zero velocity relative to Earth at the bottom of the swing and you could pick the orbit so that it picked up payloads in thin air (of course getting the payloads onto something that's rotating like that would be tricky).

Say you use it to send mass to the moon. For every 1000kg of food, fuel and people you send up, you send down 1100kg of lunar rock. This shifts the the centre of gravity of the rotating tether to a higher altitude every time two payloads are exchanged. Each end of the tether drops down to 10 or 20 km altitude, and at a low speed. Its motion relative to the ground would be mostly vertical. The amount of energy lost on each rotation would be fairly small and could be offset by importing rock from places outsi

Sadly, since a skyhook is not attached to the earth, it misses one of the key advantages of a space elevator: the earth itself supplying the necessary angular momentum. For an elevator, only potential energy must be supplied, and that rapidly gets cheaper the further up you go. Past geo-synchronous orbit it is entirely free, but velocity still increases linearly with height. (Keep in mind that the kinetic energy is proportional to the square of the velocity; paying for that energy directly is very expens

The cable spins end over end. Attach masses to both ends at the same time. One mass at the top of the arc, the other mass at the bottom. Both masses match velocity with and end of the cable. During a half rotation the two masses exchange momentum.

Easier to build because it is shorter, and because stresses are lower it can be made with materials available today. A proper space elevator still requires the development of new materials. Stress on the skyhook would be complicated by the changing gravity gradient as it rotates, but it should be easy to model.

The article suspects a space elevator could be built for $18 Billion? And they're worried about doing a study to explore who will pay for it? That much money is budget dust for any major country. Once the technology is there, I'm sure Boeing or Bechtel will be more than happy to take taxpayer money to work on the project and "create jobs."

That number is way lowballed. What, are they thinking the price of the nanotube cable is comparable to the market price of carbon?

Anyone dumb enough to pay to build a space elevator this early in the game will lose their money.

Seriously, it's an elevator from the ground to one point in geosynchronous orbit. A payload released at almost any other altitude will need reaction mass to establish a stable orbit, most of which will be expended in the direction of the cable and thus wear it down. (The exceptions ar

The article suspects a space elevator could be built for $18 Billion? And they're worried about doing a study to explore who will pay for it? That much money is budget dust for any major country. Once the technology is there, I'm sure Boeing or Bechtel will be more than happy to take taxpayer money to work on the project and "create jobs."

Anyone interested in this issue should read the NIAC report http://www.spaceelevator.com/docs/521Edwards.pdf [spaceelevator.com] which discusses the issues in detail and the technical problems. Space elevators would make space travel much cheaper. But the technical issues are immense. The NIAC report carefully outlines the major issues and how they might be handled. We would need to make extremely high quality carbon nanotubes at an immense scale. We also would need to put into space a structure orders of magnitude larger than anything we've put in space. Indeed, a space elevator would be one of the largest physical structures ever made by humans. And the engineering hurdles, such as the problems of wind in the lower atmosphere, are massive. But there's nothing about the idea that is physically impossible. The primary issues are issues of scale. And the issues are being worked on. Right now, there's a lot of work on making carbon nanotubes of high quality in a large scale. Since such nanotubes would have many different applications there's a lot of funding for that and that will likely be extremely beneficial to humanity well before it scales up to anything near that needed for a space elevator. Since the nanotube manufacturing is the primary technical hurdle, this is a good thing. I doubt we will see a space elevator in my lifetime, but maybe my children, or their children, will see it. And on that thing ribbon, space travel will finally become as cheap as so many have envisioned it.

One of the interesting things about this conference (which I attended) is that nanoscience researchers on Friday reported substantial improvements in the ability to make carbon nanotubes. They can now "grow" 1 cm nanotube mats, which can be spun into fibers. This is a substantial improvement from even 1 year ago.

I still think that a terrestrial space elevator is a decade out, but this year has convinced me that it is coming much faster than a lot of people think.

If we actually return to the moon, might a space elevator be more practical there? Could we do that now?

There's a whole wikipedia article on the topic, but in summary, a lunar elevator would be off the shelf. Not off the shelf at your local home depot, but more like Aircraft Spruce and Specialty. Not kidding, I checked their website and they sell kevlar49 spools at about ten cents per foot for 7100 denier.

It would be fun to try on a "smaller" asteroid. Then literally hardware store products would be good enough plus the operational training would be priceless.

Since it will be shared infrastructure like our roads, the public should retain ownership rather than some for-profit corporation, and the contractors we hire to build it should be thus paid with a tax or bond. Of course the same should have been done with telecom infrastructure (and then we'd have true neutrality of the wires).

That's what happens when there's no Eisenhower figure to step up and generate consensus. Yeah, people thought Obama was gonna be that type of figure, but it's not happening. (Eisenhower was a Republican, though perhaps Republicans were less cartoonish back then and acknowledged that taxes and "socialization" were practical for some things.)

Yeah, sure. Them there socialists are out to get you. Be afraid, good citizen, be afraid, there's them there socialist boogeymen in your closet! I just stay in my European socialist hellhole and enjoy life. The US were on the road to third-world status when I worked there in the early 2000s - go ahead and slide further in to your banana republic mode, you seem to enjoy it. I just pity the decent guys over there. But hey, if you want to get out - i got two large sofas in the living room - ample space for a

All of the AAA countries have a socialist party. Socialism is to Capitalism what a Republic is to a Democracy, balance. If our founding fathers would have placed that balance into the constitution we would be in a much better place.

Our lack of progress in space exploration has more to do with losing the will than limitations of technology. We could have launched a mission to Alpha Centauri by now if we pursued project Orion with modern advances to material science and optimized computer control of propulsion. If we are not doing that, who is to say we will build a space elevator even if the technology is feasible?

Which reminds me of a story I came across once-- it was basically the journal of an explorer who left Earth to some distant system with the intent to beam information back and start the colonization of the universe. Turns out, when he [and the rest of the crew] got there, space travel had advanced so much that he was welcomed as an artifact that only historians cared about while his trip amounted to nothing more than a footnote in the history books. (Plus a little extra human interest about his wife and kid

We could have launched a mission to Alpha Centauri by now if we pursued project Orion

I don't think the plans for project Orion involved slowing down at the destination, so it would be a rather pointless exercise of zipping through the Alpha Centauri system at 0.03 c, and hopefully taking a few blurry pictures of a planet before entering interstellar space again.

I was thinking about how the energy of chemical rockets is just barely sufficient (given fuel mass) to make chemical rockets that can escape Earth's gravity well. I'm not sure of the exact headroom but my understanding is that it is fairly tight. From what I have read on the strength of nanotubes, they too are theoretically just strong enough to barely make a space elevator a possibility (if we could manage to weave them into a macro-fiber without significant losses.) If this turns out to be the case I wonder if there is a connection between these two methods and the strength of chemical bonds to overcome the gravitational potential of our planet. Need it be so that these two very different ways of utilizing bond strength achieve a similar maximum gravitational field that they can overcome? And even more speculatively could the fact that the gravitational field of the Earth is near this value be important in the suitability of it to life?

http://en.wikipedia.org/wiki/Launch_loop [wikipedia.org] Launch loops are basically a big cable, supported magnetically in a vacuum sheath, and accelerated up to high speeds (14km/s+), it could be set up as a 2000km long track along the ground, about 80km up. Since it's moving faster than escape velocity, it would appear to move away from the ground, since the ground is curving away from it faster than it's moving. so it would just need to be tethered to put it into a nice flat path, and could be magnetically looped aro

The Japan Space Elevator Association (http://www.jsea.jp in Japanese) in addition to covering technical and engineering also considers business and legal issues. And here [youtube.com] is a video from JSETEC 2011 shot in Fujinomiya City, Shizuoka Prefecture on August 7 showing a climber built by Takane Matsumoto of Team Aquarius. Certainly it's cool that something like his climber exists! I don't know how high it went but I think they were going for 600m altitude. Anyway I expect these groups would welcome anybody who wanted to investigate building a loop instead.

OP says nobody is thinking about costs. However the Japan Space Elevator Association (http://www.jsea.jp in Japanese) in addition to covering technical and engineering also considers business and legal issues. Their site says they are the only group to cover legal.I once attended a meeting of theirs and a manager from a leading aerospace company was in charge. Their website also mentions someone's estimate of about 200M USD to build a megafloater island not counting cost of the station and elevator itself.

1. What is the maximum carbon fiber ribbon length can you even make with current technologies? What is the longest length of ribbon that can be made that will support its own weight with current tech?

About an inch right now, but it can be spun. No one thinks that the SE will have 100,000 long nanotubes - they will be centimeters long. Each bond is fairly weak, but the # of bonds increase with length and so short tubes can be bonded together. The real question is, how long do the fibers have to be to have a

This is not just putting a cable in orbit. Consider a long list of stability problems [newscientist.com] inherent to any project of this type. Everything from Harmonic vibration, to Coriolis effect, to shear from solar winds and complex interactions with the ionosphere. It might take a month to lift a cable car safely. Okay for raw materials, not so great for people or perishables.

Also imagine you have a 45,000 mile long antenna that extends out into the solar wind. Can you imagine the kind of voltages and currents that this

Lots of things have sounded stupid by outsiders as demonstrated by the vilification of Galileo by geo-centrists. Should he have let them stop him?

By getting together and starting broader dialogue about the idea of creating a viable mechanism for transit these people are at least working on the 'pseudo-code' for the problem. Whether this particular idea should fail or not, the solutions presented have the potential to act as a fulcrum for broader scientific discovery. Scientific revolutions don't happen by

Don't limit your perspective. Have you seen 'Minority Report?' Their interpretation of future 'roads' is like a public mag-lev bullet train taken to the individual level. Granted, that's not necessarily the way we're progressing, but it still follows that it's a possibility. Again, this is about writing the 'pseudo-code' that might yield something positive in the future, and deriding it as a wacky idea that shouldn't be taken seriously warrants a "seriously?" itself.

yea thanks I dont get my future vision from made up bullshit in a special effects house, the age of sifi actually having a real influence on tech is gone, sifi has gotten even more outlandish with its bullshit, and tech has cought up to the point where some dev at apple thinking that compressed music in a large archive is the way of the future, is long gone.

so enjoy your movies past of futures that will never be, I personally will be doing the best I can with what is available

As just a quick example, putting a payload in orbit with rockets ranges from $4,000/kg to $40,000/kg depending on the rocket type. Estimates for the cost of electricity to move an elevator into orbit is around $220/kg with current power transfer capabilities, becoming cheaper as that

Do you know anything about space elevators? Seriously. They're a great idea. Practically speaking, they are also very difficult, but if we could build one, the cost of traveling to orbit would become relatively speaking extremely cheap (technically, the energy requirements would stay the same. But the delta-v required would become as low as we please, making very cheap and low-power sources effective). Long term, unless we find a much better way to get to space, they are very likely to be built.

I agree that that is a very stupid question. Obviously, whoever uses it would pay for its use. Aka, commercial companies, NASA, military, etc. Since lots of people want to put stuff into space, lots of people could fund its operation.Probably it would be run by a company or government who would charge for its use (preferably, there would be at least two to introduce competition). That part is relatively easy. Its construction, on the other hand, is quite a problem. Financially and technically. However, it is a very good idea. Keep in mind, 150 years ago space travel on rockets was also just an idea in a few peoples minds. Turns out it isn't such a bad idea after all.

Space junk is also a problem in GEO, because it tends to concentrate in a narrow useful orbit. The only advantage is that relative velocities are small, so damage from collisions is not as severe. On the other hand, lack of atmospheric drag keeps the junk in orbit for much longer.

The funding for the first space elevator will be so massive that it should be paid for by a consrtium of companies and government agencies. This is no different than funding other large scale projects in space (ISS for example) and if we are going to get to Mars it will be together.

If, as you suggest, it would be paid for by a large consortium of companies and governments... I think you'll find that Mars is not the target, but Jupiter is. I can almost taste the hydrocarbons already.

How about we get to the point where we can build a bridge over a valley somewhere with carbon nanotubes first. Even that is a LONG ways out. Not any of our lifetimes. And that bridge is about 10000X easier to build than a space elevator.

Not really. CF is basically "really weak nanotube". CF doesn't burn too well in a vacuum, and there are not many vandals in space, or at least you can put a guard shack at the base and be done with that issue.

There are "many" CF bridges, at least in the USA. Mostly corrosion proof, you tend to find them up north in "road salt country". I can imagine, within my lifetime, we will no longer use steel rebar in concrete.

The problem with purely CF bridges, is to stop vandals with no more than a hunting knife

The Shuttle program and the ISS alone have cost us north of $200 billion.

With a space elevator, you could conceivably haul the components to build something as large as the ISS into orbit in just a month, for less than the cost of a single Shuttle launch.

Given that the cost differential between launching on chemical rockets and hauling cargo up on a space elevator is THOUSANDS of dollars a kilogram, you can pretty much guarantee that a space elevator will turn a profit. It'll cost around $200-$300 a kilogr

It could have something to do with the price tag of maglev tech, which is a little over a brazillion gazillion trillion million dollars per mile of tracks, one way. And I am not even touching the 80 mile high bridge that will have to support it. I'd say at this stage both projects look equally practical.

A couple hundred miles of maglev track versus tens of thousands of miles of unobtanium cable exposed to micrometeorites, space debris, undamped oscillations, etc. Hmm, which is more realistic...

And I have no clue what you mean by "80 mile high bridge", except to assume that you've grossly understood how a Lofstrom loop works.

The key issues are:

1) A Lofstrom loop requires no unobtanium. It may well be *physically impossible* to create the material needed for a space elevator on Earth, let alone economically practical. After all, the strongest *invididual SWNTs* measured thusfar were barely over 60GPa at the density of graphite, when you need a *bulk cable* that's ideally over 100GPa at graphite densities, preferably over 120.

2) A Lofstrom loop transmits power (the primary lift cost from both systems) at about 50% efficiency. A space elevator beams power at a couple percent efficiency. Hence a Lofstrom loop costs an order of magnitude less to operate.

So we're back to the start. Why a space elevator, apart from the fact that everyone knows of it through sci-fi? Wait, I think I answered my own question.

Yep, you're right, I did not perceive the genius at first, I just lazily looked at the picture. In fact, there is no bridge, the structure sustains itself by its own momentum, gravlevitating or whatever. Good luck building that kind of structure without Unobtainium and at only the small price I quoted in my previous post. A 80-km tall bridge won't be much harder.

A running loop would have an extremely large amount of energy in the form of linear momentum. While the magnetic suspension system would be highly redundant, with failures of small sections having essentially no effect at all, if a major failure did occur the energy in the loop (1.5Ã--1015 joules or 1.5 petajoules) would be approaching the same total energy release as a nuclear bomb explosion (350 kilotons of TNT equivalent), although not emitting nuclear radiation.

While this is a large amount of energy, it is unlikely that this would destroy very much of the structure due to its very large size, and because most of the energy would be deliberately dumped at preselected places when the failure is detected. Steps might need to be taken to lower the cable down from 80 km altitude with minimal damage, such as parachutes.

Therefore for safety and astrodynamic reasons, launch loops are intended to be installed over an ocean near the equator, well away from habitation.

The published design of a launch loop requires electronic control of the magnetic levitation to minimise power dissipation and to stabilise the otherwise under-damped cable.

The two main points of instability are the turnaround sections and the cable.

The turnaround sections are potentially unstable, since movement of the rotor away from the magnets gives reduced magnetic attraction, whereas movements closer gives increased attraction. In either case, instability occurs.[3] This problem is routinely solved with existing servo control systems that vary the strength of the magnets. Although servo reliability is a potential issue, at the high speed of the rotor, very many consecutive sections would need to fail for the rotor containment to be lost.[3]

The cable sections also share this potential issue, although the forces are much lower.[3] However, an additional instability is present in that the cable/sheath/rotor may undergo meandering modes (similar to a Lariat chain) that grow in amplitude without limit. Lofstrom believes that this instability also can be controlled in real time by servo mechanisms, although this has never been attempted.[edit] Competing and similar designs

In works by Alexander Bolonkin [7][8][9] it is suggested that Lofstrom's project has many non-solved problems and that it is very far from a current technology. For example, the Lofstrom project has expansion joints between 1.5 meter iron plates. Their speeds (under gravitation, friction) can be different and Bolonkin claims that they could wedge in the tube;[citation needed] and the force and friction in the ground 28 km diameter turnaround sections are gigantic. In 2008[10], Bolonkin proposed a simple rotated close-loop cable to launch the space apparatus in a way suitable for current technology.

Another project, the space cable, is a smaller design by John Knapman that is intended for launch assist for conventional rockets and suborbital tourism. The space cable design uses electrodynamic levitation rather than electromagnetic levitation and discrete bolts rather than a continuous rotor, as with the launch loop architecture. John Knapman has also mathematically shown that the meander instability can be tamed.[11]

For extra credit:

- Come up with necessary security measures for a 2000 kilometers long and 80 kilometers high structure which doubles as a rail-gun and which acts just like an atomic bomb if something goes wrong.- Practice saying "But there would be no radiation even if it DID explode" in front of a mirror.- Come up with a reason why is it somehow NOT impossible to build 80 kilometers long anchor cables, but stacking tho

Unobtanium? Graphene is already known to exceed the tensile strength required for a space elevator. Get with the program. Nanotubes are 90's tech. Now all we have to do is get mass production methods running, at which point the ribbon becomes trivial, though the deployment and climbers remain troublesome. I personally like the idea of simply attaching the "climber" to the ribbon at the base station, and letting the centripetal force of the earth push the ribbon out into space along with the climber, br

The other problem with a space elevator is that it's rather impractical to build a small one. If you don't go out to geostationary orbit, it doesn't work very well.

On the other hand, imagine a small Lofstrom loop (or similar device) that goes only a mile or two high. Next, imagine placing it at an amusement park (e.g. Disney World), and letting guests ride it all the way up and down (at sub-orbital speeds, of course). That's one heck of a Ferris wheel! (The current tallest Ferris wheel in the world is o

A space elevator is essentially a static structure, it does not require any power to stay in place. As such, it is more like a building than a machine. It's much less complex, which means quality control would be much simpler/possible. There are many questions about how you would build a launch loop too. The only real question about a space elevator is the material. They think single walled carbon nanotubes could be strong enough to do the trick. That means the technology is more likely to pan out in the long run. And if you could build it, it could be much cheaper to operate and much simpler to build than a launch loop.

So, in short, the space elevator gets more attention because it is a more compelling proposition, and seems more likely to succeed.

The elevator would be under an enormous amount of tension, moving it to avoid debris is not realistically possible. The plan I'd heard was to make it a thin strip so that debris would puncture only a small part of it, and then design it is such a way that it would be repairable over time. Also, you may have noticed that putting a cable under a lot of tension renders it significantly less flexible.

From my cursory understanding of space elevators, the section in geostationary orbit will have the most tension (and subsequently the most cross-sectional area for handling that tension), and the center of mass will be at geostationary orbit, which possibly involves a tether going down to Earth and something else of equal mass in high Earth orbit. Presumably, the weight of the lower end will be canceled by the centrifugal force of the upper end.

That's really a problem, you need to expend energy to keep the satellite in orbit and you need to have energy to raise the payload. Which unfortunately, is liable to be source of the fuel to keep the satellite in orbit. If you've got another means of fueling the satellite to keep it in orbit, you're probably going to be better off using that to get things into space.

Trying to use cable under tension in a scenario like this is never going to work without a major revision to the laws of thermodynamics. It is

I think the idea is stuff crawls up the outside in a more efficient manner than a rocket throwing stuff out the back and if enough cargo goes up then more can be more than would be possible merely with the fuel for the rockets used at the top or other point to keep the entire thing in station.Of course the fanboys never get as far as even considering that! It's all free energy to them because rotation confuses them and they forget that gravity is going to be greater than outward acceleration on such a stru

The whole point of a space elevator is that the centre of mass of the cable is at geosynch orbit (well slightly past it). There is no need to continuously thrust to hold the cable up because the rotational speed of the planet will fling away the cable.

The reason that the cable stays up is the gravity drops off by the square of the distance but distance travelled by the cable per hour at any height increases. The period of rotation is always 24 hours (give or take some lean) but the circumference descri

My understanding is that centrifugal forces, combined with ION engines (or similar) would keep the satellite station up and in place. Of course, this sort of design requires the cable be nearly twice as long as it actually needs to be, and sending the other half out to suck up weight (through centrifugal force). Or even anchoring some dark matter (whatever is heavy enough) to the far end which we send out to high orbit. Also, I think you seem to be under a mistaken impression about the amount of force ge

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1 meter long graphene ribbons have been synthesized, and the length of those ribbons are only limited by the fact that it was a lab scale experiment. In a few years, graphene will be mass produced at rates that will make a space elevator tether trivial to produce. The tensile strength is above the required amount, and it is far FAR more reproducible than some dumb 90's tech like carbon nanotubes.